Selective deposition of noble metal thin films

ABSTRACT

Processes are provided for selectively depositing thin films comprising one or more noble metals on a substrate by vapor deposition processes. In some embodiments, atomic layer deposition (ALD) processes are used to deposit a noble metal containing thin film on a high-k material, metal, metal nitride or other conductive metal compound while avoiding deposition on a lower k insulator such as silicon oxide. The ability to deposit on a first surface, such as a high-k material, while avoiding deposition on a second surface, such as a silicon oxide or silicon nitride surface, may be utilized, for example, in the formation of a gate electrode.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/188,087 filed Jul. 21, 2011, which is a continuation of U.S.application Ser. No. 12/649,817 filed Dec. 30, 2009 and issued as U.S.Pat. No. 7,985,669, which is a continuation of U.S. application Ser. No.11/376,704, filed Mar. 14, 2006 and issued as U.S. Pat. No. 7,666,773,which claims priority to U.S. provisional application No. 60/662,144,filed Mar. 15, 2005 and to U.S. provisional application No. 60/662,145,filed Mar. 15, 2005, each of which is hereby incorporated by referencein its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Conductive thin films can be selectively deposited by vapor depositionprocesses, such as by atomic layer deposition type processes. Such filmsfind use, for example, in integrated circuits (IC) and magneticrecording media.

2. Description of the Related Art

Thin films of ruthenium and other noble metals can be used in a widevariety of applications including integrated circuits and magneticrecording media. For example, ruthenium may be used as an electrodematerial in transistors, particularly those where silicon oxide isreplaced by high-k dielectrics. They can also be used as copper seedlayers in metallization processes. Noble metals are advantageous becausethey tend not to oxidize or otherwise corrode.

Noble metal films can also be used for capacitor electrodes of dynamicrandom access memories (DRAMs). Noble metals are also a potentialelectrode material for nonvolatile ferroelectric memories.

In addition to electrode applications, thin noble metal films findpotential use in magnetic recording technology. Inanti-ferromagnetically coupled recording media, for example, a thin Rufilm may be used for separating two ferromagnetic layers.

SUMMARY OF THE INVENTION

Thin films of noble metals can be selectively deposited using vapordeposition processes, such as atomic layer deposition (ALD). In someembodiments, a preferred ALD process comprises alternately contacting afirst surface and a second surface of a substrate with a noble metalprecursor and a second reactant, such that a thin noble metal film isselectively formed on the first surface relative to the second surface.The first surface may be, for example, a high-k material, a metal or aconductive metal compound, such as a metal nitride or metal oxide. Thesecond surface preferably comprises a lower k insulator, such as a formof silicon oxide or silicon nitride. For example and without limitation,the second surface may comprise SiO₂ or silicon oxynitride. The atomiclayer deposition reactions are preferably carried out at a temperatureless than about 400° C., more preferably less than about 350° C.

In some preferred embodiments, a gate electrode is formed by a methodcomprising depositing and patterning a gate dielectric layer andselectively depositing a noble metal such as ruthenium over the gatedielectric layer by a vapor phase deposition process, preferably anatomic layer deposition process.

In other preferred methods for forming a gate electrode on a siliconsubstrate, an interface layer is formed on the substrate. The interfacelayer may comprise, for example, silicon oxide or silicon nitride. Alayer of high-k material is deposited over the interface layer andpatterned. Ruthenium or another noble metal is selectively depositedover the high-k material by a vapor deposition process, more preferablyan atomic layer deposition process.

ALD processes for depositing noble metal preferably comprise contactingthe substrate with alternating and sequential pulses of a noble metalprecursor, such as a ruthenium precursor, and a second reactant, such asan oxygen precursor. The noble metal precursor is preferably acyclopentadienyl compound, more preferably an ethyl cyclopentadienylcompound, such as Ru(EtCp)₂.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1-6 are schematic cross-sections of partially fabricatedintegrated circuits, illustrating a process flow for the formation of agate electrode utilizing a selective noble metal deposition process.

FIGS. 7-9 are schematic cross-sections of partially fabricatedintegrated circuits, illustrating another process flow for the formationof a gate electrode utilizing a selective noble metal depositionprocess.

FIGS. 10-15, 16A, 16B and 16C are schematic cross-sections of partiallyfabricated integrated circuits, illustrating a gate-last process flowfor the formation of a gate electrode utilizing selective noble metaldeposition.

FIGS. 17-23 are schematic cross-sections of partially fabricatedintegrated circuits, illustrating another gate-last process flow for theformation of a gate electrode utilizing selective noble metaldeposition.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Ruthenium thin films and thin films comprising other noble metals can beselectively deposited on a substrate by vapor phase depositionprocesses, such as atomic layer deposition (ALD) type processes. Thesubstrate includes at least a first surface and a second surface, whichdiffer in material composition and properties. The first surface ispreferably susceptible to the vapor phase deposition process, such as anALD process, used to form the desired noble metal layer while the secondsurface is substantially insensitive to the same deposition process. Asa result, the noble metal is selectively deposited on the first surfacerelative to the second surface. In some embodiments deposition occurs onthe first surface but not on the second surface. However, although thefilm is deposited selectively on the first surface, some deposition onthe second surface is possible. Thus, in other embodiments depositionoccurs to a greater extent on the first surface than the second surfacein a given time.

At temperatures less than 450° C., noble metals are readily deposited onmany high-k materials, metals, metal nitrides, and other conductivemetal compounds from vapor phase reactants. For example, they can bedeposited by ALD. However, they are not readily deposited on lower kmaterials, such as silicon oxides and silicon nitrides. Thus, inparticular embodiments, a thin film containing noble metal isselectively deposited on a first surface comprising a high-k materialwhile avoiding deposition on a second surface comprising a lower kinsulator such as a silicon oxide, silicon nitride, silicon oxynitride,fluorinated silica glass (FSG), carbon doped silicon oxide (SiOC) ormaterial containing more than 50% of silicon oxide. In other embodimentsthe thin film comprising one or more noble metals is selectivelydeposited on a first surface comprising a metal, metal nitride, metalcarbide, metal boride, other conductive metal compound or mixturesthereof, while avoiding deposition on a second surface comprising aninsulating material., such as a low k insulator In preferred embodimentsan ALD type process is employed to selectively deposit the noble metalcontaining film.

“High-k” generally refers to a dielectric material having a dielectricconstant (k) value greater than that of silicon oxide. Preferably, thehigh-k material has a dielectric constant greater than 5, morepreferably greater than about 10. Exemplary high-k materials include,without limitation, HfO₂, ZrO₂, Al₂O₃, TiO₂, Ta₂O₅, lanthanide oxidesand mixtures thereof, silicates and materials such as YSZ(yttria-stabilized zirconia), BST, BT, ST, and SBT.

Metals, metal nitrides, metal carbides, metal borides, conductive oxidesand other conductive metal compounds that can serve as substratematerials over which noble metals can be selectively deposited mayinclude, for example and without limitation, selected from the groupconsisting of Ta, TaN, TaC_(x), TaB_(x), Ti, TiN, TiC_(x), TiB_(x), Nb,NbN, NbC_(x), NbB_(x) Mo, MoN, MoC_(x), MoB_(x), W, WN, WC_(x), WB_(x),V, Cr, Fe, Cu, Co, Ni, Cd, Zn, Al, Ag, Au, Ru, RuO_(x), Rh, Pt, Pd, Ir,IrO_(x) and Os.

While illustrated in the context of formation of a gate electrode byALD, the skilled artisan will readily find application for theprinciples and advantages disclosed herein in other contexts,particularly where selective deposition is desired with high stepcoverage.

ALD type processes are based on controlled, self-limiting surfacereactions of the precursor chemicals. Gas phase reactions are avoided byfeeding the precursors alternately and sequentially into the reactionchamber. Vapor phase reactants are separated from each other in thereaction chamber, for example, by removing excess reactants and/orreactant by-products from the reaction chamber between reactant pulses.This may be accomplished with an evacuation step and/or with an inactivegas pulse or purge.

Briefly, the substrate is loaded in a reaction chamber and is heated toa suitable deposition temperature, generally at lowered pressure.Deposition temperatures are maintained below the precursor thermaldecomposition temperature but at a high enough level to avoidcondensation of reactants and to provide the activation energy for thedesired surface reactions. Of course, the appropriate temperature windowfor any given ALD reaction will depend upon the surface termination andreactant species involved. Here, the temperature is also maintained lowenough to ensure the selectivity of the deposition process. Preferably,the temperature is below about 450° C., more preferably below about 350°C., as discussed in more detail below.

A first reactant is conducted into the chamber in the form of gas phasepulse and contacted with the surface of the substrate. Preferably thedeposition process is self-limiting. For ALD embodiments, conditions areselected such that no more than about one monolayer of the precursor isadsorbed on the substrate surface in a self-limiting manner. Excessfirst reactant and reaction byproducts, if any, are purged from thereaction chamber, often with a pulse of inert gas such as nitrogen orargon.

For ALD embodiments, the second gaseous reactant is pulsed into thechamber where it reacts with the first reactant adsorbed to the surface.Excess second reactant and gaseous by-products of the surface reactionare purged out of the reaction chamber, preferably with the aid of aninert gas. The steps of pulsing and purging are repeated until a thinfilm of the desired thickness has been selectively formed on thesubstrate, with each cycle leaving no more than a molecular monolayer.

As mentioned above, each pulse or phase of each cycle is preferablyself-limiting. An excess of reactant precursors is supplied in eachphase to saturate the susceptible structure surfaces. Surface saturationensures reactant occupation of all available reactive sites (subject,for example, to physical size or “steric hindrance” restraints) and thusexcellent step coverage.

According to a preferred embodiment, a noble metal thin film isselectively deposited on a first surface of a substrate relative to asecond surface by an ALD type process comprising multiple pulsingcycles, each cycle comprising:

-   -   pulsing a vaporized noble metal precursor into the reaction        chamber to form a molecular layer of the metal precursor on the        first surface of the substrate,    -   purging the reaction chamber to remove excess noble metal        precursor and reaction by products, if any,    -   providing a pulse of a second reactant, such as an oxygen,        ozone, ammonia or ammonia plasma product containing gas onto the        substrate,    -   purging the reaction chamber to remove excess second reactant        and any gaseous by-products formed in the reaction between the        metal precursor layer on the first surface of the substrate and        the second reactant, and    -   repeating the pulsing and purging steps until a noble metal thin        film of the desired thickness has been formed.

The noble metal thin film typically comprises multiple monolayers of asingle noble metal. However, in other embodiments, the final metalstructure may comprise noble metal compounds or alloys comprising two ormore different noble metals. For example, the growth can be started withthe deposition of platinum and ended with the deposition of rutheniummetal. Noble metals are preferably selected from the group consisting ofPt, Au, Ru, Rh, Ir, Pd and Ag.

The substrate can comprise various types of materials. Whenmanufacturing integrated circuits, the substrate typically comprises anumber of thin films with varying chemical and physical properties. Inpreferred embodiments, at least one surface of the substrate isinsensitive to the vapor phase deposition reaction. Preferably, thissurface comprises a form of silicon oxide or a silicon nitride, such assilicon oxynitride. At least one other surface of the substrate issensitive to the deposition reaction and may be, for example and withoutlimitation, a dielectric layer, such as aluminum oxide or hafnium oxide,a metal, such as Ta, or a metal nitride, such as TaN. Further, thesubstrate surface may have been patterned and may comprise structuressuch as nodes, vias and trenches.

Suitable noble metal precursors may be selected by the skilled artisan.In general, metal compounds where the metal is bound or coordinated tooxygen, nitrogen, carbon or a combination thereof are preferred. Morepreferably metallocene compounds, beta-diketonate compounds andacetamidinato compounds are used. In some embodiments a cyclopentadienylprecursor compound is used, preferably a bis(ethylcyclopentadienyl)compound.

When depositing ruthenium (Ru) thin films, preferred metal precursorsmay be selected from the group consisting ofbis(cyclopentadienyl)ruthenium, tris(2,2, 6, 6-tetramethyl-3,5-heptanedionato)ruthenium andtris(N,N′-diisopropylacetamidinato)ruthenium(III) and their derivatives,such as bis(N,N′-diisopropylacetamidinato)ruthenium(II) dicarbonyl,bis(ethylcyclopentadienyl)ruthenium,bis(pentamethylcyclopentadienyl)ruthenium andbis(2,2,6,6-tetramethyl-3,5-heptanedionato)(1,5-cyclooctadiene)ruthenium(II). In preferred embodiments, theprecursor is bis(ethylcyclopentadienyl) ruthenium (Ru(EtCp)₂).

When depositing platinum films, preferred metal precursors include(trimethyl)methylcyclopentadienylplatinum(IV), platinum (II)acetylacetonato, bis(2,2,6,6-tetramethyl-3,5-heptanedionato)platinum(TI)and their derivatives.

As mentioned above, ALD processes for depositing noble metal containingfilms typically comprise alternating pulses of a noble metal precursorand an oxygen-containing reactant. The oxygen-containing reactant pulsemay be provided, for example, by pulsing diatomic oxygen gas or amixture of oxygen and another gas into the reaction chamber. In oneembodiment, ammonia plasma products or ammonia is used as a secondreactant. In other embodiments, oxygen is formed inside the reactor,such as by decomposing oxygen containing chemicals. Oxygen containingchemicals that can be decomposed in the reactor to produce oxygeninclude, without limitation, H₂O₂, N₂O and organic peroxides. Mixturesof such chemicals can also be used. In other embodiments, the catalyticformation of an oxygen containing pulse can be provided by introducinginto the reactor a pulse of vaporized aqueous solution of H₂O₂ andconducting the pulse over a catalytic surface inside the reactor andthereafter into the reaction chamber. The catalytic surface ispreferably a piece of platinum or palladium.

In preferred embodiments the oxygen-containing reagent comprisesfree-oxygen or ozone, more preferably molecular oxygen. Theoxygen-containing reagent is preferably pure molecular diatomic oxygen,but can also be a mixture of oxygen and inactive gas, for example,nitrogen or argon.

A preferred oxygen-containing reagent is air.

The noble metal precursor employed in the ALD type processes may besolid, liquid or gaseous material, provided that the metal precursor isin vapor phase before it is conducted into the reaction chamber andcontacted with the substrate surface. “Pulsing” a vaporized precursoronto the substrate means that the precursor vapor is conducted into thechamber for a limited period of time. Typically, the pulsing time isfrom about 0.05 to 10 seconds. However, depending on the substrate typeand its surface area, the pulsing time may be even higher than 10seconds. Preferably, for a 300 mm wafer in a single wafer ALD reactor,the noble metal precursor is pulsed for from 0.05 to 10 seconds, morepreferably for from 0.5 to 3 seconds and most preferably for about 0.5to 1.0 seconds. The oxygen-containing precursor is preferably pulsed forfrom about 0.05 to 10 seconds, more preferably for from 1 to 5 seconds,most preferably about for from 2 to 3 seconds. Pulsing times can be onthe order of minutes in some cases. The optimum pulsing time can bereadily determined by the skilled artisan based on the particularcircumstances.

The mass flow rate of the noble metal precursor can be determined by theskilled artisan. In one embodiment, for deposition on 300 mm wafers theflow rate of noble metal precursor is preferably between about 1 and1000 sccm without limitation, more preferably between about 100 and 500sccm. The mass flow rate of the noble metal precursor is usually lowerthan the mass flow rate of oxygen, which is usually between about 10 and10000 sccm without limitation, more preferably between about 100-2000sccm and most preferably between 100-1000 sccm.

Purging the reaction chamber means that gaseous precursors and/orgaseous byproducts formed in the reaction between the precursors areremoved from the reaction chamber, such as by evacuating the chamberwith a vacuum pump and/or by replacing the gas inside the reactor withan inert gas such as argon or nitrogen. Typical purging times are fromabout 0.05 to 20 seconds, more preferably between about 1 and 10, andstill more preferably between about 1 and 2 seconds.

The pressure in the reaction space is typically between about 0.01 and20 mbar, more preferably between about 1 and 10 mbar.

Before starting the deposition of the film, the substrate is typicallyheated to a suitable growth temperature. Preferably, the growthtemperature of the metal thin film is between about 150° C. and about450° C., more preferably between about 200° C. and about 400° C. Thepreferred deposition temperature may vary depending on a number offactors such as, and without limitation, the reactant precursors, thepressure, flow rate, the arrangement of the reactor, and the compositionof the substrate including the nature of the material to be deposited onand the nature of the material on which deposition is to be avoided. Thespecific growth temperature may be selected by the skilled artisan usingroutine experimentation in view of the present disclosure to maximizethe selectivity of the process.

The processing time depends on the thickness of the layer to be producedand the growth rate of the film. In ALD, the growth rate of a thin filmis determined as thickness increase per one cycle. One cycle consists ofthe pulsing and purging steps of the precursors and the duration of onecycle is typically between about 0.2 and 30 seconds, more preferablybetween about 1 and 10 seconds, but it can be on order of minutes ormore in some cases.

Examples of suitable reactors that may be used for the deposition ofthin films according to the processes of the present invention includecommercially available ALD equipment such as the F-120® reactor, Pulsar®reactor and EmerALD™ reactor, available from ASM America, Inc ofPhoenix, Ariz. In addition to these ALD reactors, many other kinds ofreactors capable of ALD growth of thin films, including CVD reactorsequipped with appropriate equipment and means for pulsing theprecursors, can be employed for carrying out the processes of thepresent invention. Preferably, reactants are kept separate untilreaching the reaction chamber, such that shared lines for the precursorsare minimized. However, other arrangements are possible, such as the useof a pre-reaction chamber as described in U.S. application Ser. No.10/929,348, filed Aug. 30, 2004 and 09/836,674, filed Apr. 16, 2001,incorporated herein by reference.

The growth processes can optionally be carried out in a reactor orreaction space connected to a cluster tool. In a cluster tool, becauseeach reaction space is dedicated to one type of process, the temperatureof the reaction space in each module can be kept constant, which clearlyimproves the throughput compared to a reactor in which is the substrateis heated up to the process temperature before each run.

Formation of Gate Electrodes Using Selective Deposition

The ability to deposit on a first surface, such as a high-k material,while avoiding deposition on a second surface, such as a silicon oxideor a silicon nitride surface, can be utilized in the formation of a gateelectrode.

Several embodiments are illustrated in FIGS. 1 through 21. Otherprocesses that take advantage of the ability to selectively depositnoble metals will be apparent to the skilled artisan.

In FIG. 1, a silicon substrate 10 is illustrated comprising a layer ofnative oxide 50. The native oxide 50 is removed by etching, leaving thebare substrate 10 as shown in FIG. 2. The surface of the substrate isthen prepared for deposition of a high-k layer by ALD, such as by thedeposition of a thin interfacial layer. For example, a thin chemicaloxide or oxynitride may be formed on the surface. In other embodiments athermal oxide is grown on the substrate. In one embodiment the thininterfacial layer is from about 2 to about 15 angstroms thick. FIG. 3illustrates a thin layer interfacial layer 100 of Silicon oxide grownover the substrate 10.

A thin layer of high-k material 200 is subsequently deposited over theinterfacial layer 100 to form the structure illustrated in FIG. 4. Thehigh-k material 200 is then patterned such that it remains over thechannel region 60 and not over the regions 70 that will become thesource and drain, as illustrated in FIG. 5. Finally, a layer of Ru 300is selectively deposited over the patterned high-k material 200 by avapor deposition process, preferably ALD, and patterned (if necessary ordesired) to form the structure illustrated in FIG. 6.

In some embodiments the Ru forms the gate electrode. In otherembodiments (not shown) another conductive material, such as a metal orpoly-Si, is deposited over the selectively deposited Ru. In someembodiments the additional conductive material is selectively depositedover the ruthenium to form a gate electrode. The additional conductivematerial may be patterned, if necessary or desired. Further processingsteps, such as spacer deposition and source/drain implantation will beapparent to the skilled artisan.

Another process flow is illustrated in FIGS. 7-9. In FIG. 7, a layer ofhigh-k material 200 is deposited over a silicon substrate 10 andpatterned. The substrate may have been treated prior to deposition ofthe high-k material 200. For example, a layer of native oxide may havebeen removed and the surface treated to facilitate high-k deposition.

A layer of silicon oxide 100 is formed over the substrate 10 and coversthe high-k material 200, as illustrated in FIG. 8. The silicon oxidelayer 100 is planarized to expose the underlying high-k layer 200. Alayer of ruthenium 300 is selectively deposited over the high-k material200 to form the gate electrode structure shown in FIG. 9. In someembodiments the Ru layer forms the gate electrode, while in otherembodiments a further conductive material may be deposited over the Ruand patterned, if necessary or desired, to form the gate electrode.

A gate-last approach is illustrated in FIGS. 10-15. FIG. 10 shows asilicon substrate 10 with a layer of native oxide 50. In FIG. 11, thenative oxide 50 is removed by etching, leaving the bare siliconsubstrate 10. A silicon oxide or silicon nitride interface layer 100with a thickness of about 2-15 Å is formed over the bare substrate 10 toproduce the structure illustrated in FIG. 12. A high-k layer 200 isdeposited, preferably by ALD, over the interface layer 100 to form thestructure of FIG. 13. This is followed by deposition of a silicon oxidelayer 400 (FIG. 14). The silicon oxide layer 400 is patterned to exposethe underlying high-k layer 200 (FIG. 15). A layer of ruthenium oranother noble metal 300 is subsequently deposited selectively over theexposed high-k layer 200 to form a gate electrode as illustrated in FIG.16A. Further process steps, such as deposition of conductor or contactmetals and patterning will be apparent to the skilled artisan.

It will be understood by the skilled artisan that the ruthenium layer300 need not fill the space over the high-k layer 200. That is, in someembodiments the ruthenium layer 300 may not reach the upper surface ofthe silicon oxide layer 400 as illustrated in FIG. 16B. In a furtherstep, a conductor 320 is deposited over the ruthenium layer 300 (FIG.16C). The conductor is subsequently polished or otherwise etched back toform the gate electrode (not shown).

In another gate last approach a silicon substrate 10 covered with nativeoxide 50 is provided (FIG. 17). The native oxide 50 is optionallyremoved, followed by deposition of a layer of silicon oxide 100 over thesubstrate as shown in FIG. 18. The silicon oxide layer 100 is etched toform a trench and the exposed surface 25 (FIG. 19) is prepared fordeposition of a high-k dielectric layer by pretreatment or deposition ofan interfacial layer 120 as shown in FIG. 20. The interfacial layer 120may comprise, for example, a thermally or chemically grown ultrathinsilicon oxide or silicon nitride. A high-k layer 200 is then depositedby a vapor deposition process, preferably by an ALD process, over theentire structure (FIG. 21). The high-k material is removed from over thesilicon oxide 100 to produce the structure illustrated in FIG. 22. Thismay be accomplished, for example, by filling the space over theinterface layer 120 with a resist material, planarizing or otherwiseetching back the resulting structure down to the top of the siliconoxide layer 100 and removing the resist material (not shown). Finally, aruthenium layer 300 is selectively deposited over the high-k layer 200by atomic layer deposition (FIG. 23).

In each of the illustrated embodiments, additional processing isperformed to produce the desired integrated circuit, as will be apparentto the skilled artisan.

Because ruthenium selectively deposits on the high-k material and not onthe silicon oxide or oxynitride, it is not necessary to mask the oxideprior to deposition of the gate electrode material in each of theseprocess flows. However, if necessary noble metal deposition can befollowed with a short wet etch or other clean up process to ensureremoval of any small amount of noble metal or noble metal compound lefton the low k insulator, such as if there is less than perfectselectivity. The process flows can also save valuable and expensivematerials and, depending on the particular circumstances, can avoid thesometimes difficult etching of noble metals or noble metal compounds.

As mentioned above, the ruthenium may form the entire gate electrode.However, in some embodiments the gate electrode comprises a furtherconductive material such as a metal or poly-silicon that has beendeposited on the ruthenium. The additional conductive material may bedeposited by ALD or by another deposition process, such as by CVD orPVD. The deposition may be selective, or may be followed by patterningsteps. Preferably, the high-k material is also deposited by an ALDprocess.

The high-k material preferably has a k value of greater than or equal to5, more preferably greater than or equal to 10, and even more preferablygreater than or equal to 20. Exemplary high-k materials include HfO₂,ZrO₂, Al₂O₃, TiO₂, Ta₂O₅, Sc₂O₃, lanthanide oxides and mixtures thereof,and complex oxides such as silicates, yttria-stabilized zirconia (YSZ),barium strontium titanate (BST), strontium titanate (ST), strontiumbismuth tantalate (SBT) and bismuth tantalate (BT).

The following non-limiting examples will illustrate the invention inmore detail.

EXAMPLE 1

Ruthenium thin films were deposited on 300 mm wafers with variousmaterials formed thereover from alternating pulses ofbis(ethylcyclopentadienyl)ruthenium (Ru(EtCp)₂) and oxygen (O₂) at atemperature of about 370° C.

The pulse length of the evaporated ruthenium precursor was about 0.7seconds and was followed by a purge with an inert gas that lasted fromabout 2 seconds. The pulse length of the oxygen-containing reactant wasabout 2 seconds and the purge thereafter was about 2 seconds.

Ruthenium was found to grow using this process on TaN, Al₂O₃, Ta andHfO₂ surfaces. The typical growth rate was about from 0.5 to 0.9Å/cycleon these surfaces, not counting incubation time. The incubation time forRu growth was found to be about 50-100 cycles on TaN, 50-100 cycles onAl₂O₃, about 50 cycles on Ta and virtually zero on HfO₂.

However, even 450 cycles of the same Ru process did not produce ameasurable and conductive film on a thermal silicon oxide surfaceproduced by a wet oxide process.

Where deposition was observed, the rate was independent of the Ru(EtCp)₂dose, indicating that film growth proceeded in the self-limiting mannerthat is characteristic of ALD.

Although the foregoing invention has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art. Moreover, although illustrated in connectionwith particular process flows and structures, the skilled artisan willappreciate variations of such schemes for which the methods disclosedherein will have utility. Additionally, other combinations, omissions,substitutions and modification will be apparent to the skilled artisan,in view of the disclosure herein. Accordingly, the present invention isnot intended to be limited by the recitation of the preferredembodiments, but is instead to be defined by reference to the appendedclaims.

We claim:
 1. A method for selectively depositing a thin film comprising one or more noble metals on a substrate comprising a first surface and a second surface, the method comprising: contacting the first and second surface of the substrate with a gaseous noble metal precursor; providing a second reactant gas pulse to the reaction chamber; and repeating until a thin film of a desired thickness is obtained selectively on the first surface relative to the second surface, wherein the first surface comprises a material selected from the group consisting of metals, metal nitrides, metal carbides, metal borides, conductive oxides and mixtures thereof; and wherein the second surface comprises a material selected from the group consisting of silicon oxides, silicon nitrides, silicon oxynitrides, fluorinated silica glass (FSG), carbon doped silicon oxide (SiOC) and materials containing more than about 50% silicon oxide and wherein the temperature is below about 400° C. 